The present invention relates to an integrated circuit and a method for producing a composite comprising a tested integrated circuit and an electrical device.
Integrated circuits or semiconductor devices in wafer level packages (WLP), in contrast to standard packages, are constructed on a complete, i.e. as yet nondivided, silicon wafer. One advantage of this arrangement is the possibility that the individual, already packaged integrated circuits can already be tested at the wafer level in a parallel process.
Connecting devices or elements e.g. from a package to a printed circuit board in the case of DRAM units or packages used in flip-chip technology have to satisfy two principle requirements: firstly, the DRAM packages must be tested after the packaging of the semiconductor chips or dies. Therefore, the connecting device is used to produce a temporary contact with the test printed circuit board. In order to equalize the height deviations, a connecting device that is flexible or compliant in the Z direction, i.e. normal to the surface of the package, has many advantages. By way of example, an inexpensive test printed circuit can be used on account of the simple contact method by means of a pressure contact-connection with deformation of the flexible connecting device. Expedient testing of the integrated circuit or semiconductor device at the wafer level is possible only with flexible connecting devices or contact-making devices.
The second requirement made of a connecting device consists in providing an electrical contact with a printed circuit board, a further integrated circuit or a module board. It should have a good electrical conductivity and compensate for mechanical stresses which occur on account of the different thermal expansion of chip and printed circuit board, which are normally also supported by a filling material, and has to provide for fixed, robust linking to the printed circuit board or the other integrated circuit.
Standard connecting elements, such as e.g. solder balls, can only ever satisfy one of the two requirements, but not both simultaneously. Solder balls are usually used as fixed connecting devices. With an underfiller they constitute a reliable contact. In order to increase the reliability in the case of connecting elements of the second level, i.e. for permanent electrical linking e.g. to a printed circuit board, rings made of a polymer around the solder ball are known. The strength of a package would already be avoided by the solder balls without an underfiller. During the component test, complex clamp mechanisms have to be used in the case of such an arrangement. For a test at the wafer level, no solution is known with solder balls as connecting devices.